Offshoreonly.com - thinking about LS swap from twin 454???

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This weekend i just swapped my original Merc 377 (6.2) out of my 2009 Pachanga for a new all aluminium GM crate 6.2 Supercharged LSA engine (556HP & 551TQ). Used original Merc bell housing with a Ram Clutches conversion flywheel ($300ish) & the original motor mounts with LS adapter mounts all in the factory holes into stringers. I'd add pictures but I'm too new I need more posts lol. Anyways all bolted up easy...

Quote:

Originally Posted by 15x (Post 4657589)

Nice. Performance?

Still waiting on headers & a few other things to finish up. Or if your asking it is a GM Performance crate engine yes.

Quote:

Originally Posted by 15x (Post 4658741)

Still waiting on headers & a few other things to finish up. Or if your asking it is a GM Performance crate engine yes.

I have been looking at those motors, did you buy the marine version? Link to where you got it?

No I did not buy the marine version as the marine unit has the less desirable intercooler. The motors are identical from the block to crank, rods, pistons, cam, heads, etc... Only information i couldn't find out about is the head gaskets. I'm running a closed cooling system as I'd think most would on an Aluminium block so there will be no issues with raw water/salt corrosion.

Quote:

Originally Posted by 15x (Post 4658767)

are you going to run wet exhaust? If so, what is it?

Quote:

Originally Posted by XtremeCFM (Post 4656317)

Hey guys, i have a scarab panther 30' that i have the twin 454ci motors out of it, i was going to build them up NA to make about 680ish hp.
Im a LSX guy here and prepare many LS builds, head porting and specialize with the LSA's LS9's LS7's, LS3's and so on, big with the cts-v's and zr1's.
So im up in the air if i should just keep it simple and build up the original motors or swap out for the new tech....i can put together a pair of stock bottomend ls3's that make roughly the same in power, but just curious if others have done the swap and what have they seen different with their boat in performance and economy?
Im sure the ls motors would use half the fuel, but will the boat be a total dog and not have enough ass behind it to get it up and going.
Any insight would be great.
Thanks
Tony

A NA 680hp 6.2 liter would be a dog in a decent size boat and you better have dry headers on it with the amount of cam that would have. Need to make torque in the midrange, i dont think they really need it at 2500 because everyone turns at least 3000 just putting them on plane but to really accelerate need to make equivalent or better torque in the 3500-4500 rpm area than the 502 etc they are replacing. Might be able to match that at peak but not below there with wild cam timing. Boost is the answer I think, Im doing LSA topped 6.0s in my Donzi